Ok, so I managed to fix the no signal to monitor problem by removing and replacing the CMOS battery on the motherboard.
However, the issue still resides. I've noticed that the artifacts occur in other games like Starcraft 2 as well. The GPU temperatures during these sessions seems to be around 70~79ºC. Is that enough to overheat the GPU?
My friends have suggested baking the card to redo the soldering. Does anyone have any experience with that?